Joins & APPLY

  1. INNER JOIN β€” Join two tables with matching keys; basic patterns.
  2. OUTER JOINs β€” LEFT/RIGHT/FULL joins, handling unmatched rows.
  3. CROSS/OUTER APPLY β€” Per-row subqueries/TVFs; choose CROSS vs OUTER APPLY.
  4. 🚧 Join Strategies β€” Hash, merge, and nested loops β€” recognition & when they appear.
  5. 🚧 Anti-join Patterns β€” NOT EXISTS vs LEFT JOIN/IS NULL.